The present invention relates to thermal printing systems and, more particular, to a thermal printing transfer ribbon cassette.
It is of particular interest to apply thermal printing techniques to postage meter printing and like applications. In order to apply thermal printing techniques to postage meter indicia printing there are basically two printing options. The first is to use a full matrix thermal print head to print the entire postage indicia simultaneously. A second option is to use a line matrix thermal print head. The use of a line matrix thermal print head for postage meter printing applications is preferred due to the reduced cost as compared against a full matrix thermal print head.
In order to use a line matrix thermal print head, it is considered advantageous to use thermal ribbon cassette in combination with a rotating platen. Generally, a suitable configuration includes a postage meter base having an envelope transport which include a rotatively driven platen. The line matrix thermal print head and thermal ribbon cassette are mounted to the base such that an envelope is captured between the platen roller and the thermal ribbon with the thermal print head serving as a backing. The platen roller applies a biasing force such that rotation of the platen roller cause the envelope to travel in the print direction.
In a novel thermal printing postage arrangement, the platen action is used to drive both the envelope and cassette ribbon past the thermal print head in this manner the opportunity for print smearing is minimized. In this configuration it is necessary to assure that the print ribbon remains taut in order to derive a thermal print divorced of any smears. Conventionally, the thermal ribbon cassette employes a spring loaded wheel which traps the ribbon against a stationary member. However, the conventional design can produce ribbon wrinkle.